VATICAN CITY—Bringing to a close a scandal that has rocked the Roman Catholic Church and upset millions of its followers, trusted Sistine Chapel janitor Giuseppe Falduto, 78, was convicted Thursday of sexually abusing four popes between 1965 and 2011.

The widely publicized trial revealed that Falduto, well regarded and affectionately referred to as "Beppe" by Vatican City residents, had over a period of six decades frequently exploited his position to compel Pope Paul VI, Pope John Paul I, Pope John Paul II, and Pope Benedict XVI to engage in unwanted sexual activity.

"The crimes committed by Mr. Falduto are of course shocking and deplorable," said Dean of the College of Cardinals Angelo Sodano, adding that he had never previously suspected "kindly old Beppe" of any wrongdoing. "But perhaps most upsetting is the fact that this man gained the trust of high-ranking church authorities and then betrayed that trust by secretly defiling innocent popes."

"These appalling acts caused tremendous psychological trauma for his victims, and we are currently reexamining our internal policies to safeguard the current and future papacy," Sodano continued. "Even one pope molested is one too many."

In June 2011, after receiving a tip about suspected pontiff abuse from a Vatican groundskeeper, police raided the Sistine Chapel and discovered hundreds of sexually explicit Polaroid images of popes in a shoe box Falduto kept under his cot in the basement.

Investigators confirmed the incriminating materials included distressing photographs of Pope John Paul II in his underwear lifting up his robe, Pope Paul VI engaged in sodomy, Pope John Paul I wearing sunglasses and posing nude in a beach chair, and a crying Pope Benedict XVI covered in semen.

Police also reportedly seized a garbage bag full of old miters apparently collected by the elderly janitor and kept hidden in a broom closet.

Richard Blevins, a psychologist and consultant to the International Conference of Catholic Bishops, said the decades-long cycle of sexual abuse likely would have continued if no one had reported the misconduct, because in most pope abuse cases it is often difficult for the Vicar of Christ and Successor to St. Peter to speak up about what has happened to him at the hands of a trusted adult.

"Many popes feel deeply ashamed and are afraid that if they try to talk about the abuse, no one will believe them," Blevins said. "It's important to keep an eye out for the common signs of papal molestation, such as the Holy Father avoiding direct eye contact while saying mass or becoming shy and withdrawn during an audience with foreign dignitaries."

Added Blevins, "I've talked to cardinals who say that in hindsight, there did always seem to be something wrong with each of the last four Popes whenever the janitor was mopping up nearby."

Despite physical evidence collected from the boiler room of the papal residence, the prosecution's case against Falduto hinged on Pope Benedict XVI's emotional testimony, during which he told the jury the custodian had on numerous occasions lured him downstairs with the promise of gifts such as original manuscripts of the Gospel of St. John or Mars candy bars.

Benedict described in graphic detail the molestations that occurred behind the Sistine Chapel altar, as well as Falduto urging His Holiness to touch and kiss his penis. The pontiff also said that he felt powerless, claiming the janitor threatened to tell everyone in the Catholic Church about what he had done.

Longtime coworker Salvatore Bianchi, 63, told reporters he never would have guessed Falduto was engaging in inappropriate acts.

"Old Beppe was a hardworking, reliable employee who put in long hours and appeared to really love his job," Bianchi said. "He usually stayed late enough that he'd still be there poking his head in the door whenever I was trying to give the pope his nightly bath."